In 1970, only 10 percent of vacationers traveled by airplanes to their destination. By 1990, that number had increased to 35 percent. Now, in 1970 the risk of being injured in an airline accident was 1 chance per 300 flights. Due to changes in aircraft design, this risk decreased to 1 chance per 1000 flights by 1990.
Which of the following can be properly inferred from the passage?